In the past, roofing shingles have had to satisfy two main functions when applied to a roof deck. The first function is to provide a durable, weatherproof covering for the roof deck. Roof shingles, whatever their form, are intended to provide a means of sheltering the structure below the shingles from precipitation and the deleterious effects of sun and wind. Roof shingles installed on the roof deck must perform these protecting functions for a reasonable period of time. The second function is to present an aesthetically pleasing architectural feature which enhances the overall appeal of the structure to which the shingles have been applied. This aesthetic function has been satisfied by providing asphalt shingles with various butt edge contours and surface treatments which operate to simulate more traditional, and in most cases more expensive, forms of roof coverings, such as, thatch, wooden shakes, slates, and even tiles of various forms.
Natural slate tiles have long been used as a roof covering. Natural slate is a durable material and is considered to provide an aesthetically pleasing look or appearance to a roof. Natural slate tiles have an advantage as a roof covering in that they will not burn, and therefore they can be used in dry climates where the possibility of fires precludes wood shake roofs. Natural slate tiles are applied to a roof deck or roof framework one tile at a time in a labor intensive process, but the overall appearance of the roof of the individually laid tiles is deemed by the marketplace to be worth a premium price. One of the features of roofs of natural slate is that different sources of slate have different colors. Commonly available colors are gray or green, and different colors such as red are more scarce. Therefore, slate roofs typically have a predominant color, such as gray, with one or more additional accent colors interspersed to add variety. An example of a common mix of colors for a slate roof might include roughly 60 percent of the tiles having a light gray background color, about 15 percent of the tiles having a purple color, and about 25 percent of the tiles having a dark gray color.
As an alternative to the high installed cost of natural slate, roofing suppliers have developed plastic or polymer tiles, such as highly filled thermoset resin tiles. An example of such a polymer tile in the form of wood shake shingles is disclosed in U.S. Pat. Nos. 5,615,523 and 5,711,126, both to Wells et al.
However, none of the prior art shingles have been able to combine the protective and aesthetic functions while providing a laminated, asphalt shingle that simulates a slate roof on a practical production scale.